Kanye West's debut album, "The College Dropout," which came out in 2004, was a concept album. The title referred to West, then 26 years old and already a successful hip-hop producer. The lyrics pointed out that many of his peers who had finished college weren't doing nearly so well.

In one monologue, he gives his take on the career ladder for college graduates at the Gap: entry-level position, followed by kissing up to the boss, followed by a promotion to secretary's secretary. "And boy is that great," he says. "You get to take messages for the secretary who never went to college."

I'll confess that I'm not one of the 2.5 million people who have bought the album. I was introduced to it when I was giving a talk to some college students a couple of years ago, and one of them asked whether West was right that a college degree had become overrated.

After all, even computer programmers fear outsourcing these days, and recent raises for college graduates have been meager. Yet because economists still insist education is the key to prosperity, the discussion often feels like a muddle.

Fortunately, though, there has been an enormous natural experiment on precisely this subject over the last few decades. In the experiment, one big group of Americans has become vastly more educated, while another group has not. The two have created an excellent case study.

For the sake of simplicity, let's refer to the first group as "women" and the second as "men."

From the founding of the country's first (all-male) colleges in the 17th century until just a few decades ago, men received far more education than women. But the two sexes have now switched places in a remarkably short time.

During the late 1960s and early 1970s, about one out of every three young men got a bachelor's degree. In the years that followed, the share fell somewhat, both because Vietnam War draft deferrals were no longer an issue and because college became more expensive. In the 1980s and 1990s, the share rose again.

But the shifts have been fairly small. For the last four decades, somewhere between 30 percent and 35 percent of men have graduated from a four-year college by the time they turned 35 years old.

The story is quite different for women. In the 1960s, only 25 percent received a college degree. Among today's young women almost 40 percent will end up with one. At one commencement ceremony after another this month — be it at Boston College, San Francisco State University or Colby College — women in caps and gowns outnumber men.

The relevant question is how much of a return women have gotten on their education. And the answer isn't especially subtle. The return has been enormous.

Armed with college degrees, large numbers of women have entered fields once dominated by men. Nearly half of new doctors today are women, up from just one of every 10 in the early 1970s. In all, the average inflation-adjusted weekly pay of women has jumped 26 percent since 1980.

And men? Their pay has increased about as much as their college graduation rate — it's up just 1 percent since 1980.

Education obviously isn't the only reason. Gender discrimination has become less prevalent in recent decades, and today's female college graduates are less likely than their mothers and grandmothers to choose modest-paying jobs, like teaching. The decline of manufacturing jobs, meanwhile, has disproportionately hurt men. But research by Francine Blau and Lawrence Kahn of Cornell suggests that, over the past two decades, education played the biggest role in narrowing the pay gap.

There are two statistics that I think do a particularly good job of capturing this point. The first shows that the gap between the pay of men and women with college degrees hasn't budged over the last 15 years. Full-time female workers with a bachelor's degree made 75 percent as much as their male counterparts in 1992 — and 75 percent as much in 2007.

Women still face discrimination, after all, and they're still more likely than men to become teachers. More women also choose jobs that trade some pay for flexibility and reasonable hours. (Whether this is a good thing, a bad thing or neither needs to be a subject for another day.)

Yet even though the pay gap among college graduates hasn't changed, the overall pay gap between men and women has continued to close in the past 15 years. That's because so many more women have become college graduates and earned the pay premium that a degree really does bring. Across the whole work force, full-time women made 79 percent as much as full-time men last year, up from 75 percent in 1992.

To put it another way, women would have made almost no progress in narrowing the gender pay gap over this period if they hadn't been so thoroughly trouncing men in the classroom.

And it's not as if women's gains have come at the expense of men. By becoming more educated — and able to do more productive, higher-wage jobs — women have increased the size of the economic pie. The economic growth in a country like South Korea, which has made much more educational progress than the United States, clearly demonstrates this. "If you look across countries," says Lawrence Katz, a labor economist at Harvard, "education is the strongest predictor for how quickly the pie grows."

That said, education can't solve the middle-class squeeze all by itself. Health-care costs — which have been holding down the pay gains of everyone, including college graduates — need to be brought under control, and the tax code can stand to be more progressive.

But education is vital. It directly helps those who get it, and it makes it easier for the country to afford programs that help everyone else. Yet for something that just about everyone in Washington claims to favor, education also suffers from a disturbing lack of strategic seriousness. Republicans haven't been willing to spend enough money on preschool, college financial aid and numerous other areas, while Democrats haven't been willing to hold schools and universities accountable for mediocrity.

It's almost — almost — unfair to pick on West. He's dead wrong about education, and his enormous teenage audience makes his words matter. But he isn't the main problem.